(Newser)
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Aviation experts say it could easily have been one of the deadliest air disasters of all time. An Air Canada Airbus A320 was cleared to land on a runway at San Francisco International Airport just before midnight Friday, when, to the shock of air traffic controllers and other pilots, the Air Canada pilot lined up to land on the parallel taxiway, where four other planes were waiting to take off, the San Francisco Chronicle reports. "Where's this guy going? He's on the taxiway," a voice says in a control tower recording. "An air traffic controller sent the Air Canada jet around" and the pilot landed safely after another approach, the Federal Aviation Administration said in a statement, per the Guardian.

The four planes waiting to take off were full of fuel and passengers, meaning the incident "probably came close to the greatest aviation disaster in history," Ross Aimer, CEO of Aero Consulting Experts, tells the San Jose Mercury News. The FAA is investigating what it says was a "very rare" incident. Aviation investigator John Cox, a former commercial pilot, tells the CBC that SFO requires "precision flying" because the runway and taxiway are exceptionally close together—but that doesn't explain how the pilot could have mistaken the blue lights of the taxiway for the clear lights of the runway. He says the investigation will likely focus on why technology designed to prevent collisions apparently failed.